This invention relates generally to push pad operated exit devices and more particularly to exit devices having push pads requiring minimal motion for unlatching a door.
There are basically two types of push pad exit devices used to secure the entrance of a building, namely rim lock and vertical rod lock. The rim lock latches the door on the door edge opposite the hinge edge by means of a latch bolt which projects into a strike pocket located in the vertical door frame member. The vertical rod latches the door, on the same door edge as does the rim lock, with two latches, one projecting into a strike in the top horizontal portion of the door frame and the other projecting down into a floor mounted strike. The purpose of the rim lock and vertical rod lock is to secure an entrance, such that attempts to open the door from the inside of the building without pushing on the push pad or outside of the building using the door trim will fail.
In the rim latching application, the latch bolt is rotatable about a fixed axle. As the door is shut, the latch bolt rotates to bump over a fixed strike on the door frame. After clearing the strike, the latch bolt projects into the strike pocket. The latch bolt, being spring biased into the strike, locks the door to the frame.
Additional security and tamper resistance is provided by means of a deadlocking feature which, when activated, prevents the latch bolt from being retracted without the use of the push pad or trim. An auxiliary bolt, which is triggered by the closing of the door, enables the deadlocking feature when the auxiliary bolt is pressed into the door by the proximity of the door edge to the door strike. Deadlocking, which is maintained as long as the door remains closed, results from movement of a component within the push pad device which allows a blocking member to drop by gravity into a position to prevent the latch bolt from being externally manipulated or forced out of the strike to open the door. When the push pad is depressed, the auxiliary bolt is disengaged along with the deadlocking feature, and the latch bolt is physically retracted out of the strike pocket to open the door.
In vertical rod latching, a push pad on the inside of the door retracts the vertical latch bolts out of the strikes when pushed. The latches are normally spring biased into the strikes located in the floor and header of the frame. The vertical rod design requires some mechanism for keeping the latch bolts retracted inside the door once the door is open and the push pad is released since, while the push pad is depressed, both latch bolts are held in their retracted states. However, upon release of the push pad, the door begins to close, and the bottom latch drags on the floor. To prevent this drag, the top latch has a feature inside which keeps the latch bolts in the retracted position until the door closes. The top latch bolt is set in the retracted position by depressing the push pad, and the bottom latch bolt is physically connected to the top latch bolt by a series of linkages. The bottom latch bolt is held retracted by means of the linkages and the mechanism in the top latch responsible for setting the top latch bolt in the retracted position. A pin in the frame door stop depresses a trigger in the top latch as the door closes releasing the latch bolts into the strikes to lock the door.
Deadlocking, in the vertical rod applications, is accomplished by means of complicated timing of lever arms to block the latch bolts from external manipulation. These blocking mechanisms are, at best, capable of one to three latch bolt stopping positions. A latch in a vertical rod application incorporates a blocking member to prevent the latch bolt from being retracted by external means without the use of the push pad. When the door is closed, the extended position of the latch bolt allows a spring biased lever inside the latch to move into a position capable of blocking the latch bolt. This spring biased lever can have one to three steps which allow blocking of the latch bolt at three different extensions thereof. These different extensions of the latch bolt are required to account for the varied bottom door gaps encountered in the field. The push pad, when depressed, moves the blocking lever out of the path of the latch bolt to allow withdrawal of the latch bolt and opening of the door.
Both the rim latching and the vertical rod latching systems have disadvantages, namely, the gravity drop deadlocking design of the rim latching system is very sensitive to manufacturing tolerances and is prone to unreliability and field failures if not diligently monitored by the manufacturer. In the vertical rod system, the top latch is used to hold itself and the bottom latch retracted through a series of linkages and moveable components. As a result, any unavoidable play or clearances in the linkages accumulates in the bottom latch once the push pad is released, and the bottom latch will drag on the floor and must be adjusted independently by manipulation of the bottom rod. This is a serious drawback, in that field installation people usually do not have the expertise required to make these adjustments correctly. Since the deadlocking feature in the latches is dependent upon the air gap between the bottom of the door and the strike lip located in the floor, it becomes almost critical. The gap can vary between 1/4" and 3/4' and dictates different latch bolt extensions into the floor strikes. Since there are commonly only one to three deadlocking positions to allow adjustment for varying door bottom gaps and tolerance stack-up in the linkages, the quality of the deadlocking function is questionable.
The method of latch retraction is an objectionable feature which also relates to both rim lock and vertical rod lock systems. Latch retraction in both systems requires depression of the push pad by at least 3/4 inches in order to provide sufficient motion in the retraction mechanism of the device to fully retract the latch bolt. When the push pad is not depressed, it projects outwardly from the door, interferes with passage of equipment through the doorway, and even lends itself to damage. In addition to its undesirable aesthetics, the large amount of motion for bolt retraction is accompanied by a proportionately large amount of noise and wear of the assembly.
The foregoing illustrates limitations known to exist in present push pad operated panic exit devices. Thus, it would be advantageous to provide an alternative directed to overcoming one or more of those limitations. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.